Manufacture of photographic plates for use in printing-presses.



UNITED STATES PATENT OFFICE.

STEFAN EPSTEIN, OF PARIS, FRANCE.

MANUFACTURE OF PHOTOGRAPHIC PLATES FOR USE IN PRINTINGPRESSES.

SPECIFICATION forming part of Letters Patent No. 717,369, dated December30, 1902.

Application filed February 3, 1902- Serial No.92A28. (No specimens.)

ter at 70 centigrade, twenty-five grams hard T aZZ whom, it may concern:

(photographic) gelatin, ten grams of a bichro- Be it known that I,STEFAN EPsTEIN, a sub- I jectof the Russian Emperor, and a resident of78 Rue de lAssomption,Paris, France,have invented certain new and usefullm provemeu ts in the Manufacture ofPhotographic Plates for Use inPrinting-Presses; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame, reference being had to the accompanying drawings, and to lettersof reference marked thereon, which form a part of this specification.

Photomechanical processes hitherto known are not suitable for use inconjunction with printing-presses, with the exception of autotypeandline-engraving, which two processes have also various disadvantages,the principal of which is that satisfactory half-tones cannot beobtained,while in the case of autotype there are the additionaldisadvantages that pure white must be avoided and'that the finer detailsare lost. While, therefore, attempts have been made to use photographicplates in printing-presses, these have been unsuccessful, because, onthe one hand, the glass plate is notsufficiently resistant, and, on theother hand, the printing-film does not adhere sufficientlywell to theglass plate.

A metalplate prepared according to this invention has the followingcharacteristic features: First, the emulsion adheres permanently andfirmly to the metal plate; second, the film on the plate is unusuallytough; third, the film can be produced on the plate in any desiredthickness, so that representations even in high relief and capable ofbeing molded can be produced; fourth, theplate can be exposed "beneathany ordinary photographic glass or film negative (without ruled screen.)

Metal plates according to this invention may be prepared in thefollowing manner: The metal plate (preferably a copper one) is firstroughened by any known process, and after being freed from grease anddirt is heated to atemperature of from 45to centigrade, or thereabout.An emulsion prepared as hereinafter described is then spread uniformlyon the plate. The ingredients of which the emulsion is composed arepreferably as follows: One hundred and twenty grams distilled wamate'(preferably the bichromate of potash or ammonia) or a mixture of severalbichromates, forty-five to fifty cubic centimeters alcohol, and anamount not exceeding one cubic centimeter of acetic acid. When theemulsion has been poured on the hot plate, (whose temperature at thisstage is about 50 centigrade,) the plate is gradually further heated toa temperature of about to centigrade, for example, but not exceeding 100centigrade, after which it is allowed to cool slowly. In the meantime,assuming that copper plates and acetic acid are both used, acetate ofcopper is formed between the metal plate and the emulsion and effects anintimate union of the plate and the film. When other metals than copperare used, the corresponding acid must be used to form the correspondingsalt.

A plate prepared as above described is then exposed under a negative. Bythis treatment those places which are most strongly lighted becomeperfectly hard and insoluble in Water, while those places which are moreor less strongly lighted become more or less hard and in such conditionas to swell either more or less when water is applied to the same.The,plate having been exposed is now moistened by permitting water toflow over the same, whereby the parts are caused to swell, according totheir capability for swelling, as described. The plate is then ready foruse.

When required to be used for printing, the plate or film is moistened,preferably by impregnating it in a vacuum with glycerin as free fromwater as possible. It is then placed in an ordinary printing-press-as,for example, a high-speed press-and copies printed therefrom in theusual manner. The print ing-ink is accepted and retained uniformly bythe hardened portions, while as to those parts which are more or lessswelled this is the case only in quantity corresponding to suchswelling. In this manner the hard port-ionsthat is to say, those partsstrongest lighted under the negativeproduce a deep black in the copy orprint, while the more or less swollen portions (those parts more or lessstrongly lighted under the negative) produce,

corresponding to the ink taken by the same, from half-tones to purewhite.

The treatment of the printing-plate with glycerin and water underexclusion of air imparts to the plate such a property that it can beused for printing in a high-speed printingpress without moistening theplate after each impression, which latter operation would be required ifthe plate were treated with water alone instead of with glycerin andwater in a vacuum. By treatment of the plate with glycerin and waterunder exclusion of air a highlyfavorable result is obtained, inasmuch asthe remoistening of the plate is only necessary after about each fivehundred copies made.

By the use of the three ordinary colorplates, as well understood, theprocess can of course be employed for three-color printing.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent of the United States of America, is-

1. The process herein described of making heliotypographic plates foruse in book-printing presses, which consists in roughening the surfaceof a plate of suitable metal, heating said plate to about 50 centigrade,covering the plate with a mixture of hot water, gelatin, a bichromate,

pure alcohol, and a suitable acid, heating the plate and said mixturethereon to about 100 Centigrade, permitting the plate to cool, exposingthe same to light under a negative, washing the plate with water, andthen treating the same with a mixture of glycerin and water,substantially as set forth.

2. The process herein described of making heliotypographic plates foruse in book-printing presses, which consists in roughening the surfaceof a plate of suitable metal, heating said plate to about 50 centigrade,covering the plate with a mixture of hot water, gelatin, a bichromate,pure alcohol, and a suitable acid, heating the plate and said mixturethereon to about 100 centigrade, permitting the plate to cool, exposingthe same to light under a negative, washing the plate with water, andthen treating the same with a mixture of glycerin and water in a vacuum,substantially as set forth.

, In testimony that I claim the foregoing as my invention I have signedmy name in presence of two subscribing witnesses.

STEFAN EPSTEIN.

Witnesses:

MORITZ RAPP APORT, LEO MAAsit.

